Rotary device



Allg 12, 1958 H. R. NlLssoN 2,847,157

ROTARY DEVICE Filed oct. 26. 1954 United States Pater-rt ROTARY DEVICE*Hans Robert Nilsson, Ektorp, Sweden, assignonby'mesne assignments, toSvenska `Rotor Maskiner Aktiebolag, Nacka, Sweden, a corporation ofSweden Application October 26, 1954, Serial No.i464,689 Claims-priority,application Sweden October l27 ,M1953 15 Claims. (Cl."230"-1'43) VThepresent invention relates to arotary vdevicecornip'rising a casing andenclosed therein` aV set of rotors having 'cooperating lands and.grooves, which casing-with'ajacket portion encloses the rotors and isvprovided with aninlet an outlet. Therotary-device under considerationfisintended for compression or lexpansion of a gaseousm'ediumandparticularly there is contemplated:suitablerernbodiments of a rotarydevice operating .as a-low` pressure compressor.

According to the ordinary design of rotary-devices of the 'kind underconsiderationthe jacketand the-endplates "of the casing are manufacturedas separate parts. When assembling the jacket and the end platestogetherwith the rotors considerable difficulties are .encounteredLin-ad-`justin`g all parts with the required precision -andrinspite of greatestraccuracyof manufactureanexact centering of the rotors in the bores ofthe. jacket for the-rotors -an'd -the'required parallelism between therrotor shafts is diflicult to accomplish. Manufacture also is verycomplicated, expensive and time-consuming.

The invention contemplates a Asimplification and thus acost`reduction ascompared with lmethods hitherto employed for manufacturing such rotarydevices and at the same time to obtain an improved precisionfor theassembling of the parts of a rotary device operating ef- `cien`tly andsafely. This hasprimarily beenattained by providing the casing with onlyone vend plate for supporting therotors solely at one end thereof. Thecasing and 'this end plate may then be made in one piece or, ifrthey forcertain reasons in a simpler way may-be manufactured as separate partsthey may be fastened together to form a unit, whereafter turning of thebores ofthe jacket -and the bores of the end plate for the rotorsrisperformed in one and the some operation, so that an exact centering and`parallelism of the shafts hmay be secured. Sincethe' ends of the rotorsremotefrom the end plateterminate 'freely in a corresponding jacketbore,fno centeringproblems at this side will occur. Diliicultiesotherwise occurring in the coordination of a centering at one end platewith the centering at the othery end plate is thus eliminated.v t

A specic object of the invention is to eliminate as far 4'astpossibletherisks of seizing between therotors :and 'between rotor and `jacketrespectively. y

According to a-preferred form oftheinventionathe rotors are constructedin accordance -with Vthe principles set forth in the U. S. specification2Q622-,7S7 accordingfto which the lands of the male rotor are ofgenerally-V convex `cross sectionlyingsubstantially outside ofthepitchcircle of the male rotor and the lands of thefemale rotor-are ofgenerally concave cross `section lying jsubstantially "within the,pitchcircle of the female rotor. Further,` the profiles of said-landsare 4of such curvature that :upon

rotation offthe rotors the 'crest of each convex land..of thermale rotorcomes into contact or spacerpackedcon- 'tact (sealingproximity) with thewallsofthe cooperating .grooveof the female rotor tata. place` insidethefpitch circle "of the female rotor. According to a modified-deend`plate 114 in vbores 44 made in .theisame `plate forms reinforcedportionsf46zaround thespin'dle ends 42. Iby'means of lock nutst48-bythreading-againsttithe-reinforcements 46 offtheend plate,.theispin'dles 38, V40won the inside of the bores `44.of the endplatejforrningan #abutment 50.

Patented IAug. 12,y 1958 sign also described'in lthe said vspecificationthe major `portions of :the landsof thermalezrotor liefoutsidelthe pitchcircle of the VVmale rotor and aretofsubstantially symmetrical convexly`curved profile :andthe minorzportions of which `lie within'the`pitchfcirclaof `the male rotor and are of substantially ysymmetricallconcavely curved profile, and themajorzportions 'ofthelands'ofithe'female rotor lie within the` pitchlcircle4 of thefernale-rotor and areof substantially symmetrical'curvedproleland vthe minor portions .ofwhich lie 'outside the pitch .circle of 'the female rotor and are,` of`substantially:symmetrical vconvexly curvediprolile. :For vfurtherdetails as regards the profiles reference is madet'o'thesaidspecification. The designs 7of the profiles of thelandsi'and grooves ofthe rotors=disclosed byv said specification are particularly adaptedtothe present type of rotary devicesandtotacertain extent it may be saidthat theytaretindispensiblerin order to ensure the satisfactoryoperation of Lthe rotary -device or to render suchoperation'possibleatTall.

Other characteristic features and detailsfofthe inven- 'tion will appearfrom the description of Lan-embodiment Yrotary device, taken on the lineY3:--3 of Fig. .2.

Fig. 4 is a side elevational viewofrthexsame rotary device, `partly insection.

The rotary device shown hasV alcasing 10 fcomprisingia jacket 12 and anend plate`14 manufacturediin'one piece. The outer sides of the jacketare provided'lwi'thcooling yflanges `16. In the jacket twoboreslS and.2mal-esprovided intersecting eachother along the` lines. 22 andt24 andform the bores for a male;rotor 28 'providedwith four helical,substantially convex lands` 26,` anda female rotor -32 provided with sixhelical substantially `concave lands 30. The Imanner ofI operation ofsuchfrotary device is assumed to be known to yeveryone 'familiarawith-the art, so that thesame will-'not'.be :described :herein detail.

The`male and` female rotors '28 andzn'respectively, consist of sleeves34 and 36, respectively, reach being journalled on spindles 38 and-40,respectively,:each spindle of which With their outer kends 42 is:securedtoeithe Therfend The spindle ends are` threaded `Pand are'lockedThe rotor sleeves `34 and 36 yare journalled on;bearirrg rings which aremountedy on the spindles38,40'andmay, for example, consist of ballbearings'. or, as in .thetpresent :example of a ballbearingfSZ and-aroller :bearing-54, lthe former1being=located atthe-.low-:pressure'aendsand the'latter `at thehigh pressure-end of therotarytdevice. The bearing rings 52, 54 :are separated .'bylaa :distancesleever'56. `Toflock the rotor sleevesl34, dtothe'spindles`38, f4()against sliding, 'lockenuts-Sr are threadedton the outer ends'l) of thespindles andrestf-againstfthe ballbearings 52, Vand lockrings "62ofsteelor "iisimilar t material are recessed into :the-"ends lof 'the rotorssleeves 34, 36 facing the end'tplateflt. lThelock.ringtiZuofLthe `malerotorsleeve andthev llockfringofsthe femalezrotor fsleeve is secured by.meanswofrscrewsr-oti. Thefzlock Vrings 1621also-serve as`parts-win:aesealing1constnictionzzand b'e- 3 tween them and the endplate 14 there are mounted sealing rings 68.

The ends of the rotor sleeves 34, 36 remote from the end plate 14 arecovered by caps 70 and 72 respectively, cap 70 of the male rotor beingsecured by means of pin bolts 64 and the cap of the female rotor bymeans of bolts 74. The cap 2S of the male rotor 70 is integral with ashaft 76 which passes through a central bore 78 in the spindle 38carrying the male rotor and serving as a driving shaft for the malerotor.

According to the invention a rotary device of the kind underconsideration may be simplified as regards the construction andmanufacturing. The female rotor as shown in the example is driven by themale rotor solely by the engagement of the lands of the male rotor withthe grooves of the female rotor.

Thus the synchronizing gears may be dispensed with which otherwise havebeen necessary in order to get the female rotor to rotate with the malerotor without there being risk for seizing.

As a further measure to prevent seizing of the rotors it is suggestedaccording to the invention to make thc rotor sleeves of differentmaterials. The sleeve 34 of the male rotor accordingly is made of acompressed fibre material bound by a suitable binding-medium as forexample asbestos pressed together with suitable articial resin, such asa silicone resin, whereas the sleeve 36 of the female rotor consists ofsteel or similar ma terial. The sleeve of the male rotor may alsoconsist solely of a plastic or similar material.

In the example of the rotary device illustrated as a low pressurecompressor lthe casing forms a radiallyaxially extending outlet 80. Theinlet of the rotary device is formed by the open end 82 of the jacket 14and in order to prevent direct communication between the inlet andoutlet openings a cover plate 84 is secured by means of bolts 86 at theopen jacket end, which accordingly covers the jacket opening at least sofar that the inlet and the outlet openings are cut off from directcommunication but not more than an axial opening remains at the inlet orlow pressure side. The inlet 82 is accordingly defined by the innercontour of the rotor bores 18, and the edge profiles 88, 90, 92 of thecover plate.

The interspace between each rotor sleeve and corresponding bearingspindle is supplied with a lubricant from the outside at the end plateend of the device via a supply nipple 94 issuing into a channel 96 insaid spindle. The surplus lubricant is able to escape by means ofcentrifugal action through a gap between the rotor sleeve and thebearing spindle for the same. In the present case the rotor sleeve atthe end facing the end plate of the casing is fastened -to the lock ring62 which is sealing against the end plate of the casing by means of asealing ring 68 recessed into the end plate of the casing. Between thelock ring 62 and an enlargement on the spindle clearance is provided forescape of the surplus lubricant centrifuged off from the interspacebetween the rotor sleeve and the bearing spindle therefor. Said surpluslubricant finally escapes through an outlet channel in the end plate.The arrangement for lubrication disclosed enables an ample lubricationwithout risk of heat conduction from the rotor sleeve to the sleevespindle by means `of lubricant medium filling the entire interspacebetween the. parts. The arrangement further ensures ample lubrication ofthe bearings for the rotor sleeves.

On driving shaft 76 of the male rotor there may be provided atransmission disc. In the example shown this disc consists of a beltpulley 98 which is journalled on a ball bearing ring and a rollerbearing ring 100 and 102, respectively, mounted on the outer end 104 ofthe spindle 38 supporting the male rotor. A lock nut 106 secures thebearings 100 and 102 which are provided with a distance ring 108therebetween. The belt pulley 98 at its inner end has anabutment 110resting against `plated one.

What I claim is:

l. A helical screw device operating with a gaseous medium and comprisinga casing providing a jacket and having an inlet and an outlet openingdisposed adjacent opposite ends, a set of rotors having cooperatingconvex lands and concave grooves rotatably mounted in said casing, saidcasing being provided with only a single end plate at its high pressureend, while the low pressure end of said casing terminates freely at anopen end of the casing, spindles mounted on said end plate andprojecting into said casing and said rotors being overhung on said endplate and being journalled as sleeves on said spindles.

2. A helical screw device according to claim 1, in which the open end ofsaid casing opening is covered by a plate at least to a degree providingthat the inlet and outlet openings are cut off from directintercommunication but not more than to leave an axial opening at thelow pressure end.

3. A helical screw device according to claim l, in which said end platesupporting the rotors is formed integral with the jacket.

4. A helical screw device according to claim 1 having at least one malerotor and at least one female rotor, in which the female rotor is drivenby the male rotor merely through the engagement of lands of the malerotor with grooves of the female rotor.

5. A helical screw device according to claim l, which includes aninterspace between the rotor sleeve and rotor spindle supplied withlubricant from the outside at the end adjacent said end plate, a channelfor the lubricant formed in said spindle, and clearance being providedbetween the rotor sleeve and rotor spindle for escape of surpluslubricant centrifuged off from the interspace.

6. A helical screw device according to claim 5, which includes an escapechannel in the end plate for the centrifuged-off lubricant.

7. A helical screw device according to claim l, in which the spindlesupporting the sleeve of the male rotor is hollow and receives a drivingshaft for the sleeve of the male rotor.

8. A helical screw device according to claim l, in which the rotorsleeves are journalled on their spindles by means of ball bearings.

9. A helical screw device according to claim l, in which the rotorsleeves are journalled on their spindles by means of a ball bearing atthe low pressure end and a roller bearing at the high pressure end.

l0. A helical screw device according to claim 9, in which means areprovided to space the bearings apart and the end of the rotor sleeveadjacent the end plate carries a ring member in sealing relation withthe end plate by means of a seal entering a recess of the end plate,clearance being formed between said ring member and an enlargement ofthe spindle to allow escape of surplus lubricant centrifuged off fromthe interspace between the sleeve of the rotor and the spindle.

ll. A helical screw device according to claim l, in which the rotorsleeves are secured to the spindles by a locking ring at the end plateend of the rotor sleeves and by a lock nut at the free end of thespindles.

l2. A helical screw device according to claim ll, in which the rotorsleeves at the free ends of the spindles are covered by caps secured tothe ends of the respective sleeves.

13. A helical screw device according to claim 12, in which the cap ofthe male rotor is rotationally xed with respect to the driving shaft ofsaid rotor.

14. A helical screw device according to claim 1 in which'said set ofrotors includes a male rotor having a driving shaft therefor and whichincludes a transmission disc secured to said driving shaft journalled onthe spindle of the male rotor sleeve.

15. A helical screw device according to claim 1, in which the lands ofthe male rotor are of generally convex cross section locatedsubstantially outside the pitch circle of the male rotor and the landsof the female rotor are of generally concave cross section locatedsubstantially within the pitch circle of the female rotor, the profilesof said lands being of such curvature that upon rotation of the rotorsthe crest of each convex land of the male rotor comes into contact orsealing proximity with the walls of the cooperating groove of the femalerotor at a place disposed inside the pitch circle of the female rotor.

References Cited inthe tile of this patent UNITED STATES PATENTS

